Dynamical independence reveals anaesthetic specific fragmentation of emergent structure in neural dynamics

Summary

Conscious experience relies on neural activity coordinated across multiple scales. Using a measure called dynamical independence applied to EEG data, the study found that propofol and xenon, which abolish conscious report, produce more emergent but highly variable dynamic structure, indicating fragmented brain organization. Ketamine, which preserves dream-like states, showed reduced emergence but partial preservation of macroscopic structure similar to wake. Regional source-level contributions varied. The results dissociate the amount of emergence from its organization and caution against equating emergence with consciousness level.

Study at a glance

Abstract

Conscious experience depends on the coordinated activity of neural processes that span multiple scales—from synapses to whole-brain dynamics. A recently introduced measure, dynamical independence, identifies, characterises and quantifies these multi-scale relationships using an information-theoretic dimensionality-reduction approach. Here, we use DI to examine changes in emergent dynamical structure in the human brain under three pharmacologically-distinct anaesthetic interventions (propofol, xenon, ketamine). Applied to source-reconstructed EEG, our analysis reveals that propofol and xenon, anaesthetics that abolish conscious report, exhibit more emergent but highly variable dynamic structure, indicating fragmented macroscopic dynamical organisation. By contrast, ketamine, which preserves dream-like phenomenology, shows the opposite pattern: reduced overall emergence yet a partial preservation of the macroscopic structure, mirroring wake. Further exploratory analyses revealed spatially localised source-level contributions to emergent dynamical structure, highlighting regional variations. Together, our results highlight drug-specific reconfigurations of emergent dynamical structure under anaesthesia, dissociate the amount of emergence from the organisation of emergent dynamics, and caution against equating emergence with level of consciousness.